The median age is the age that divides the population into two equal-size groups. Half of the population is older than the median age and half is younger. Median age is based on a standard distribution of the population by single years of age and is shown to the nearest tenth of a year. (See the sections on "Standard Distributions" and "Medians" under "Derived Measures.")

The data on marital status were derived from answers to Question 4. The marital status classification refers to the status at the time of interview. Data on marital status are tabulated only for people 15 years old and over.
All people were asked whether they were "now married," "widowed," "divorced," "separated," or "never married." Couples who live together (unmarried people, people in common-law marriages) were allowed to report the marital status they considered the most appropriate. When marital status was not reported, it was imputed according to the relationship to the householder and sex and age of the person.
Differences in the number of currently married males and females occur because there is no step in the weighting process to equalize the weighted estimates of husbands and wives.

Includes people whose current marriage has not ended through widowhood, divorce, or separation (regardless of previous marital history). The category may also include couples who live together or people in common-law marriages if they consider this category the most appropriate. In certain tabulations, currently married people are further classified as "spouse present" or "spouse absent."

Includes people legally separated or otherwise absent from their spouse because of marital discord. Those without a final divorce decree are classified as separated. This category also includes people who have been deserted or who have parted because they no longer want to live together but who have not obtained a divorce.

Includes people who are legally divorced and who have not remarried. Those without a final divorce decree are classified as separated. In selected tabulations, data for married and separated people are reorganized and combined with information on the presence of the spouse in the same household.

All people whose current marriage has not ended by widowhood or divorce. This category includes people defined above as "separated."

Spouse Present

Married people whose wife or husband was reported as a member of the same household or same group quarters facility, including those whose spouses may have been temporarily absent for such reasons as travel or hospitalization.

Spouse Absent

Married people whose wife or husband was not reported as a member of the same household or the same group quarters facility.

Separated

Defined above.

Spouse Absent, Other

Married people whose wife or husband was not reported as a member of the same household, excluding separated. Included is any person whose spouse was employed and living away from home or in an institution or serving away from home in the Armed Forces.
Differences between the number of currently married males and the number of currently married females occur because of reporting differences and because some husbands and wives have their usual residence in different areas. By definition, the numbers would be the same.

The median age at first marriage is calculated indirectly by estimating the proportion of young people who will marry during their lifetime, calculating one-half of this proportion, and determining the age (at the time of the survey) of people at this half-way mark by osculatory interpolation. It does not represent the actual median age of the population who married during the calendar year. It is shown to the nearest tenth of a year. Henry S. Shryock and Jacob S. Siegel outline the osculatory procedure in Methods and Materials of Demography , First Edition (May 1973), Volume 1, pages 291-296.

Beginning in 2007, people 15 years and over who were ever married (currently married, widowed, separated, or divorced) were asked if they had been married, widowed, or divorced in the past 12 months. They were asked how many times (once, two times, three or more times) they have been married, and the year of their last marriage.

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations have marital status distributions that are very different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the marital status distribution. This is particularly true for areas with a substantial GQ population.

The word "current" was dropped from the 1996-1998 question. Since 1999, the question states, "What is this persons marital status?" The American Community Survey began providing the median age at first marriage with the 2004 data.

The data on the Hispanic or Latino population, which was asked of all people, were derived from answers to Question 5. The terms "Spanish," "Hispanic," and "Latino" are used interchangeably. Some respondents identify with all three terms, while others may identify with only one of these three specific terms. Hispanics or Latinos who identify with the terms "Spanish," "Hispanic," or "Latino" are those who classify themselves in one of the specific Hispanic or Latino categories listed on the questionnaire- "Mexican," "Puerto Rican," or "Cuban"- as well as those who indicate that they are "other Spanish/Hispanic/Latino." People who do not identify with one of the specific origins listed on the questionnaire but indicate that they are "other Spanish/Hispanic/Latino" are those whose origins are from Spain, the Spanish-speaking countries of Central or South America, the Dominican Republic, or people identifying themselves generally as Spanish, Spanish-American, Hispanic, Hispano, Latino, and so on. All write-in responses to the "other Spanish/Hispanic/Latino" category were coded.
Origin can be viewed as the heritage, nationality group, lineage, or country of birth of the person or the persons parents or ancestors before their arrival in the United States. People who identify their origin as Spanish, Hispanic, or Latino may be of any race.
Some tabulations are shown by the origin of the householder. In all cases where the origin of households, families, or occupied housing units is classified as Spanish, Hispanic, or Latino, the origin of the householder is used. (For more information, see the discussion of householder under " Household Type and Relationship .")

Beginning in 2006, the population in group quarters (GQ) is included in the ACS. Some types of GQ populations may have Hispanic or Latino origin distributions that are different from the household population. The inclusion of the GQ population could therefore have a noticeable impact on the Hispanic or Latino origin distribution. This is particularly true for areas with a substantial GQ population.